Plant or installation for extracting dust from minerals such as coal



M h 29,1933. gR. 1,903,046

PLANT OR INSTALLATION FOR EXTRAGTING DUST FROM MINERALS SUCH AS COAL Filed Nov. 17, 1930 2 Sheets-Sheet 1 March 28, 1933; 5 HUNTER 1,903,046

PLANT OR INSTALLATION FOR EXTRACTING DUST FROM MINERALS SUCH AS COAL Filed Nov; 17, 19 30 2 Sheets-Sheet 2 Patented Mar. 28, 1933 UNITED STATES PATENT OFFICE SHERWOOD HUNTER, OF N EWLYN, PENZANCE, ENGLAND PLANT R INSTALLATION FOR EXTRACTING DUST FROM MINERALS SUCH AS COAL Application filed November 17, 1930, Serial No. 496,275, and in Great Britain November 21, 1929.

This invention relates to apparatus for the extraction of dust from minerals, particularly coal, of the type in which air is blown upon or through the falling minerals.

In devices of this type previously used, the coal or other mineral (hereinafter referred to as coal) has been dropped down a chute, on one wall of which is an air inlet through which a blast is injected by suitable means (such as a fan), while in the opposite wall are fitted louvres through which the dust collected in the air stream is carried to a separate collector. The disadvantages attendant upon such anapparatus are that the air blast is not sufiiciently strong to carry away dust other than the dry dust which separates freely from the coal, so that when damp coal is dropped the dust adheres and the device is ineffective. Further the coal does not fall uniformly, and the air stream is not evenly distributed.

A further reason why this plant has not been successful is that eddies generated in the air stream by its passage through the louvres have kept the dust in circulation, with the result that some of it has been drawn back to, and clogged the fan, which works in a closed air channel. This trouble is aggravated when the air blast is strengthened to free the coal of damp dust.

The object of the present invention is to introduce means whereby the fall of the coal and the flow of the air is rendered uniform.

In carrying the invention into effect fins or partitions are fitted in the air passage between the fan and the chute, to smooth out the flow of air. In this way the removal of dry dust is greatly improvedand facili- 40 tated. To separate dust from wet coal, eX-

ternally driven rollers are provided in place of a few of the uppermost louvres; or when considered desirable, all the louvres may be replaced by such rollers, the rollers in all cases being separated to leave gaps through which the dry dust (and also wet dust, after separation) is blown. To act as air locks and prevent the undesirable passage of dustladen air, doors may be provided at the in- 50 let and/or the outlet of the chute.- Such doors are opened preferably automatically by the weight of the coal passing.

The air circuit is closed, air being drawn to the fan from the top of the dust collecting hopper. As a result of this system, unless the velocity of the air stream is kept very low dust up to a certain mesh is kept in constant circulation with the air, the mesh depending mainly on the strength of the air blast. This effect may be utilized to grade the dust by inserting between the hopper and the fan a cyclone or other suitable dust separator of any known kind. This cyclone separator collects from the air practically all the dust which has been drawn thereby past the hopper, and the mesh of the dust separately collected in this way can be controlled to any desired size by altering the strength of the air blast.

Referring now to the attached drawings representing one modification of the plant, and in which Figure 1 represents a side elevational View partly in section,

Figure 2 an end elevational View, 75

Figure 3 a plan View of the plant.

In carrying the invention into effect coal raised by a suitable elevator 1, shown diagrammatically (Figure 1) is dropped through chute 2, which has its working length sloped at a suitable angle so that the falling coal will come into contact with one wall. The wall of the chute against which the coal falls consists of members so spaced that dust or small fragments can pass between them while the coal cannot thus escape. In known apparatus of this kind these members consist of adjustable louvres; and such adjustable louvres 3 may be employed in the present invention. These louvres may be replaced by rollers 4 driven by means not shown and spaced to leave between them gaps similar to the louvred openings. The position of the louvres is so adjusted and the rollers are so driven that the dust and fragments will not 95 normally fall through the openings, but must be carried through; and to do this a fan 5 or other suitable means is provided to force an air blast through the closed channel 6 into the chute 2 through suitable openings in the 100 wall opposite to the louvres and rollers. This air blast passing across the chute carries with it dust and fragments from the coal into a hopper 7 where it is retarded by bafile plates, either fixed, such as 8, or pivoted about their upper edge, such as 9. The dust so retardec falls into the hopper 7 and passes out through a suitable exit 10; while the air stream proceeds through the exit 11 and along a closed return passage to the fan 5.

The main difliculties previously experienced were that unevenness of the air blast and local congestion of the falling coal prevented efficient separation of the dust; and this could not be improved by increasing the strength of the air blast since this caused Violent disturbance of the dust in the hopper and hence choking of the outlet.

In the present invention these difficulties are overcome by inserting in the chute 2, above the sloping working portion, baiiles 13 (see also Figure 2) made, for example, of angle iron, which cause the mixed coal and dust to fall evenly and prevent any local congestion. To distribute the air evenly and smooth the flow, the tunnel 6 between the fan 5 and the chute 2 is for example formed of two portions 14 and 15. Section 14 is shaped so that while the floor and roof remain parallel along its entire length the walls are divergent; while section 15 is formed to join sec tion 14 but shaped so that its floor and roof are divergent while the walls run parallel to one another. (See Figures 1 and In section 14 are fitted fins or partitions such as 16 (Figure 3) which stand vertically and are so spaced and arranged divergently as to spread the air evenly horizontally through this section. In a similar manner section 15 is fitted with fins or partitions 17, the edges of which come into contact with the fins 16 of section 14 horizontally, i. e. at right-angles to the edges of the fins 14, so that where fins 16 and 17 meet a honeycomb is formed. The fins 17 then extend forward divergently, as shown in Figure 1, to spread the air stream further in a uniform manner vertically. These fins 16 and 17 thus prevent unnecessary turbulence and vortices, without unduly restricting the passage, as would be done, for example, if the usual honeycomb were employed. Such a restriction might cause blocking of the passage by dust. In order to deflect the air stream it and when desired the fins 17 are fitted at the ends near the chute with adjustable lips 18, pivoted about suitable points as shown.

In order further to ensure that the air flow remains steady and even, a door such as 19 may be fitted to the inlet of the chute. This prevents any air escaping up the chute. Such a door is preferably hinged and held closed by a balance weight 20, as shown, to be opened automatically when the weight of the coal above it reaches a certain prearranged value. A similar door may be fitted at the outlet 21 of the chute, so that since the dust outlet 10 is sealed by the dust falling through it the air stream must then pass through the outlet 11 and along the closed passage, suitably sloped to prevent the dust lodging therein and obstructing the path, and so back to the fan.

This fact that the air is carried through a closed circuit, is used in one modification of the invention to great advantage. It will be realized that although the dust collected, as described above, in hopper 7 is not useless. its immediate use is impaired by its unhomogeneous mesh so that it has to be graded before it can be used.

In the modification referred to this grading is carried out by the plant at the same time as the coal is freed of the dust. To do this there is introduced in the air channel between the outlet 11 and the fan 5 a cyclone separator of any suitable known type, which will 1"ree the air almost completely of the dust it carries. This modification is shown in dotted lines 22 in Figures 1, 2 and 3. When this modification is inserted the ve locity of the air stream is increased to such an extent that the lighter particles of dust, up to some prearranged mesh, will not fall into the hopper 7 but will be carried by the air through the outlet 11. If necessary some or all of the bafiie plates 19 may be removed; and it is obvious that by so doing and by adjusting the wind speed, large dust particles can be made to fall in the hopper 7 while the smaller particles will be carried to and collected in the separator 22. In this way grading of the dust can be effected as desired.

From the above description it will be clear that in the invention is disclosed a plant which separates dust from coal in a very efficient manner, even when it is wet. The efficiency is further greatly improved by the smoothing of air flow and the even distribution of the falling coal overcoming difiiculties which previously had caused the employment of such plant to be discarded. Finally a great advantage is obtained in the means provided for grading the dust during the one handling for use as fuel or for other purposes. These improvements add enormously to the eflicacy and value of the device.

Having now described my invention what I claim as new and desire to secure by Letters Patent is A dust extraction plant comprising in combination, a sloping chute through which passes the material to be freed from dust, louvres in one wall of said chute, a fan producing an air blast, a first divergent chamber for said air blast, such chamber having parallel horizontal top and bottom walls and divergent side walls, partitions arranged with in said chamber, a second divergent chamber arranged in series with the first chamber, and

having parallel vertical side walls and divergent top and bottom walls, partitions in such chamber arranged at right angles to the partitions in the first chamber, the small end of such first chamber being connected to the fan, the larger end of the second chamber forming one wall of the said chute.

In testimony whereof I have signed my name to this specification.

SHERWOOD HUNTER. 

